Process for the removal of nickelkieselguhr catalysts from hydrogenated butadiene polymers



PROCESS FOR THE REMOVAL OF NICKEL- KIESELGUHR CATALYSTS FROM HYDRO- GENATED BUTADIENE POLYMERS Martin R. Cines-and'Ben BrBuchanan, 'Bartlesville, Okla,

ssignors toPhillips Petroleum Company, a-corporation of Delaware No'Drawing. Application March'2 5, 1955 Serial No. 496,932

9 Claims. (cum-85.1

This invention relates to the removal of the hydrogenation catalyst from a solution of a hydrogenated polymer of butadiene. In a further aspect, this invention relates to the removal of nickel-kieselguhr catalyst from a solution of hydrogenated .polybutadiene dissolved in a solvent by a .process comprising diluting said solution with an additional quantity of solvent, heating the resulting mixture and removing the catalyst from the heat-treated'mix- -ture by filtration or by centrifuging the mixture. V

A copending application of Jones and Moberly, Serial No-395,291, filed November 30, 1953, discloses a process for the production of thermoplastic materialspre 'pared by hydrogenating rubbery polymers of .butadiene. These materials are especially valuable for arctic service because of the fact that they are flexible at very low temperatures. Broadly, however, theyareused to make fibers, filaments, dishes, containe'rsffilms, sheetingsftoy's, gaskets, tubing, coating materials, protective coverings, White sidewalls for tires, andmany other materials.

The hydrogenated polymers areprepared by a catalytic hydrogenation procedure. 'In cariying out this process, a butadiene polymer, substantially free of salts or other materials which might act as hydrogenation catalyst poisons, is fed to a hydrogenation reactor in a form of a solutionor dispersion in a suitable solvent. lnsome instances, the polymers dissolve completely, while in othereasesea dispersion is formed and this appears to be "afunction of the particular polymer.

'The polymers used in producing these new thermo- :plastic materials are selected from rubbery 'ho'mopolyme'r s of butadiene and copolymers of butadiene and styrene :using not over 30 parts by Weight of styrene ,per -l= parts by weight of monomers. These polymers are prepared by emulsion, polymerization, the temperature for th'etpolyrnerization ranging from F.-to-l 40"F.,-.pref- 'erably from 20 F. to 60 F. Polymers of butadiene produced at 4 1 F. haveproduced hydrogenated materials with the best balance ofproperties. Thevpolymerto be hydrogenated-should have ;a Mooney viscosity below 40 (ML4) measured at 212 F., although polymers of high Mooney viscosity can be used followingmilling or other degradation of the polymer prior to hydrogenation.

The catalyst'used-in this process is a nickel kieselguhr catalyst having aparticle size between -1 to 8 microns which has been activated at a temperaturebetWeen-SOO and 800 'F. for-a period of several hours bypassing hydrogen thereover. Catalysts of larger particle size can --be;used but they are =not-as satisfactory. One'catalyst,

which is found to be quite suitable, 'is such a nickelkieselguhr catalyst treated at 675 F. -for4 hours using approximately 100 volumes of hydrogen per volume of catalyst. Such treatment provides -a reduced nickel content of approximately 40 percent. .-From2-to 30 weight percent of the catalyst on'the unreducedbasis based upon fulges.

the weight of the polymer ives arpreferred rate of hydrogenation.

As stated above, many solvents can be used, but the ones Which we have used to the greatest extent are the cyclopara'fiins'containing 5 or 6 carbon-at0ms in the ring and "their 'alkyl derivatives. Solvents such as cyclopentane,

'i'riethylcyclopentane, cyclohexa ne, and met-hylcyclohexane are representative of these solvents. .Mixtures of these solvents can also beused. "Furthermore, it is not'necess'a ry to use the pure cycloparaffimthe commercialgrades being satisfactory. For example, the commercial grade of cyclopentane has been found to contain cyclopentene wen as paraflins such as 2,2 dimethylbutane, normal p'en'tau'e, and diis op'ropyl. Commercial'methylcyclopenare toluene, normal he'ptan'e, and small amounts of cis- 1,2-dimetliylcyclopentane. After thepolymeris dissolved .in the solvent, the hydrogenation'catalys't is added. The

frnixture is introduced into a reac torghydrogen is added, and the'teinper'a't'ure raised to a suitable level to initiate the reaction. This operation can be carried out in a ib'a'tch i vi'se or a continuous process. Reaction pressures are' preferably in the range of atmospheric to3000 p. 5. i. g.,

thehsual'range being within 1'00 to 1000p. isfi. .g. The

"temperature ean ran' e from 7-5 F. u to the degradation temperature of the polymer "or "the critical temperature j'of the "solvent, i'n'aximu'm temperatures ranging as high "as 575 F. The preferred range is between 300 and-525 [Re actientimes in the rang of lto 24 hours, pref- '-"e;ab1' 2 to 12 hours, are employed.

"Inorder to obtain polymers of the desired'characteristics, the unsaturation should be reduced to a value of approximately f0 to '50. percent, based upon thetlieo retical value of percent for the 'unhydrogenated-polymer.

P'referabl'ythe hydrogenation is continueduntil the resid- 40 ual unsatura'tion is less than 30 percent.

One difiiculty which has been encountered in carrying out this process 'i's'th'e rernoval of the enarys't'nem the reactor' efiluent. The initial polymer and the hydrogenfa-ted product both have a very high a'fiin'ity forthe solvent. Therefore, only fdilute solutions can be used, solutions containing 3to 15 percent polymer by "weight beinggenerally used. It is preferable to wof'kwith "solutions containing approximately 5 weighte percent of the polymer. Even with these dilute solutions, the removal of the finely divided nickel-kieselguhr catalyst is extremely diflicult. Some magnetic separators have been-used but "we are not aware of any which are suitable for large capacity operation. Also, certain mixtures have been obamed which "are practically impossible to separate by ordinary methods of "filtration or by high speed ,ceritri- For instance, "one of'th'ese solutions was treated in a G equals the force of gravity. Complete removal of .i the catalys'tcofild not be eflected even when this force is applied. i

' The following are objects of this invention. An object of this invention is to .provide aprocess for the removal of finely divided nickel-kieselguhrfrom asolution of hydrogenated polybutadiene. A further object of this invention is to provide hydrogenated butadiene polymers free of catalyst.

Other objects and advantages of this invention will be apparent to one skilled in the art upon reading the accompanying disclosure.

We have discovered that a particular sequence of steps will permit removal of this finely divided catalyst from the polymer solution. Broadly, these steps comprise diluting the solution with an additional quantity of the solvent, heating the resulting mixture and then removing the catalyst from the heat-treated mixture. These steps of diluting and heating the mixture result in agglomeration of the catalyst particles. Following this agglomeration, the catalyst particles settle out of the solution and can be removed therefrom by conventional procedures. As set forth above, the solution to be hydrogenated should contain 3 to 15 percent polymer by weight, although solutions containing about 5 percent polymer are preferred. The amount of solvent added in the dilution step is preferably in an amount to give a 2:1 ratio based upon the volume of the material from the reactor containing the original amount of solvent, the polymer, and the catalyst, This is the optimum ratio although the ratio of additional solvent to reactor efiluent can be in the range of 1:1 to 5:1. The temperature for the heating operation is from 100 to 575 F. although we prefer to operate in the range of 300 to 400 F. The heating is carried out under pressures up to 3000 p. s. i. g. to prevent loss of the solvent. The time can be broadly set forth as minutes to 8 hours, although 30 minutes to 4 hours constitutes the preferred heating time. It will be apparent to one skilled in the art that there is a relationship between the original polymer concentration, the

amount of additional solvent added, the temperature, and the time of treatment. With dilute solutions, less additional dilution is required. Likewise, as the amount of dilution increases, the severity of the heating, including both the temperature and length of time, can be lessened. Finally, heating at a high temperature for a short period of time appears to bring about the same result as heating at a low temperature for a long period of time. The preferred conditions set forth above are believed to provide the best balance of conditions for commercial operation.

It is usually preferable to add an additional quantity of the same solvent as that used for the hydrogenation process because the solvent recovered can then be recycled to the hydrogenation process. However, if desired, the additional solvent can be different from the solvent present during the hydrogenation.

The following examples set forth certain representative data from runs which have been made in the development of this invention and should be considered in that light rather than as limiting the invention to the conditions set forth therein.

Example I A series of butadiene polymers were prepared by emulsion polymerization at 41 F. using the following recipe:

Parts by weight The following tabulation shows the amount of polymer, amount of modifier, and the time conversion data for this series.

Modifier, Conver- Mooney Run parts/ Time, ston. .\1 [r4 parts hours percent at butadiene 212 F.

The products were combined to give 30 pounds of polymer having a Mooney (ML-4) of 21 at 212 F.

Using 45 gallons (295 pounds) of methylcyclohexane as a solvent, 15 pounds of this polybutadiene were dissolved and 3 pounds of a nickel-kieselguhr catalyst having a reduced nickel content of 43.9 percent were added. This mixture was introduced into a reactor and contacted with hydrogen for 3 hours therein, the reactor pressure being 505 p. s. i. g. and the temperature being 404 F. The residual unsaturation of the hydrogenated polymer was 14.3 percent following the hydrogenation. The particle size of the catalyst ranged from 1 to 15 microns. The viscosity of the reactor efiluent was approximately 10 centipoises at 100 F. Because of the dispersed catalyst, the product was black in color and light could not be transmitted therethrough. The reactor efiluent was heated to a temperature of F. and fed to a centrifuge at a rate of ml. per minute, this centrifuge operating at 21,000 R. P. M. The product obtained from this run was black in color and unsatisfactory for further use. The material was also centrifuged in a special laboratory centrifuge operating at a bowl speed of 50,000 R. P. M. (60,000 G) in an attempt to remove the catalyst solids therefrom. The material from this run had some of the catalyst removed but was still gray in color and unsatisfactory for use.

Therefore, centrifuging alone was not satisfactory for this particular material.

Example 11 based on polymer) 0.15 Antioxidant: Polygard (percent based on polymer) A5 in Example I.

A conversion of 57 percent was obtained in 18.5 hours, the resulting polymer having a Mooney viscosity of 16 (ML4) at 212 F.

A 14.6 pound portion of this polymer was dispersed in 45 gallons of methylcyclohexane and 3 pounds of the finely divided nickel-kieselguhr catalyst, having a reduced nickel content of 35.9 percent, was added. A resulting mixture was heated in the presence of hydrogen at 403 F. at 500 p. s. i. g. for 3 hours. The resulting hydrogenated polymer had an unsaturation of 13.1 percent. Portions of the reactor effluent were treated with various materials and heated for varying lengths of time. The

results of these treatments are shown in the following used because it is capable of applying greater force for the separation process, this emphasizing the difficulty of table:

Catalyst Heat and I slllullly, Additions to Slurry, ml. Time Time to Settle Observations 30 Xylene, 30 ml 460 F. iorl overnight.-. During heating, no change was obhour. served. After overnight settling about 1" :at top 11" total) had settled out. 15 Xylene, 15 1111.; E 0, 400 F."for2 Developed a leak, but no apparent 16 ml. hours. change occurred in slurry and no catalyst settled in water phase. 15 Methylcyclohexane, 30 300 F. for4 none required. At the end of 4 hours, the mixture ml. hours. cleared, the catalyst stuck to walls and settled. After cooling andshaking, the catalyst separated by settling in a short time. .OgH OH, m1 362 F. for l 2 hours No settling was observed.

our. Methylcyclohexane, 26 360 F. for 1 overnight. No settling had occurred after 2'hours. ml. hour. After overnight was well settled and another 1%" partially settled. Methyloyclohexane, 30 385 F. for 2 1% hours Solution partially cleared after 1% ml. hours. hours of heating. The particles did not settle rapidly but coagulation could be seen and after heating, light was transmitted through the solution.

Example III A 15 pound portion of the polybutadiene of Example II was dispersed in 45 gallons of methylcyclohexane and 2.25 pounds of finely divided nicke'l-kieselguhr catalyst were added. This mixture was treated with hydrogen for 3 hours ata-temperature of 402 F. at a pressure of 501 p. s. i. g. A polymer having an unsaturation of 15.9 percent was produced.

An attempt was made to remove the catalyst from the reactor effluent with a centrifuge but separation was impossible. One part by volume of this solution was then diluted with 2 parts of methylcyclohexane. The re-v sulting solution was heated to 350 F. in 3 hours and maintained at 350 F. for 1 hour. This treatment caused the catalyst particles to agglomerate and they could be removed in a centrifuge. When the catalyst was subjected to 8,000 G at a temperature of 120 F., 100 percent clarification was effected. Centrifuges of this type are commercially available.

The exact mechanism of our invention is not fully understood. Apparently, the addition of the additional solvent and the heating affects the solution in such a way that the particles of the catalyst lose their attraction for the solution and agglomerate. It is known that this is not simply an efiect caused by diluting the solution since, without the heating step, the separation is not improved. Furthermore, it is not due to the viscosity reduction due to the higher temperature because the slurry can be cooled following the agglomeration of the catalyst particles and the catalyst can still be removed from the slurry as long as the temperature is maintained above that at which the polymer gels, i. e., above 85 F. and preferably above 100 F. However, this invention does solve a problem which has been a serious bottle neck in the production of the hydrogenated polymers.

As set forth in Example II, it is possible to observe the effect of the treatment by noting the settling of the catalyst particles. An additional method which we have used is to pass the material through a Jerguson gauge having two clear sight glasses and provided with a 15-Watt fluorescent bulb behind the gauge. Before treatment, no light is transmitted through the inch light path of the gauge. As the treatment continues, a point is reached when light passes through the gauge and, at this point, the particles have been sufiiciently agglomerated so that they will settle out on standing or will be removed by the use of a centrifuge.

While the examples set forth herein have been based upon the use of a centrifuge as the test apparatus, it is apparent that filtration can also be used following agglomeration of the catalyst particles. The centrifuge is the catalyst removal. Also, where the agglomeration is continued for a considerable period of time, separation by simply decanting the clear solution from the catalyst can be'used.

As many possible embodiments .may be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not as unduly limiting the invention.

We claim:

1. In the process forproduction of hydrogenatedmaterial by hydrogenating polymeric material selected from the group consisting of rubbery homopolymers of butadiene and copolymers of butadiene containing not over 30 percent by weight of styrene wherein said polymeric material is dispersed in a cycloparafiinic hydrocarbon solvent and contacted with hydrogen in the presence of a finely divided nickel-kieselguhr catalyst in order to reduce the unsaturation of said polymeric material; the method of removing said catalyst comprising diluting the dispersion of said hydrogenated polymeric material, solvent, and catalyst, with an additional quantity of a cycloparaflinic hydrocarbon solvent, said additional cycloparaffinic solvent being added in an amount of 1:1 to 5:1

I based on the volume of said dispersion; heating the resulting mixture at a temperature of to 500 F. for 10 minutes to 8 hours, the time of said heating being sufficiently long to cause agglomeration of said catalyst; and removing said catalyst from the heat-treated mixture.

2. The process of claim 1 wherein said catalyst is removed by filtration.

3. The process of claim 1 wherein said catalyst is removed by centrifugation.

4. The process of claim 1 wherein said polymeric material is a homopolymer of butadiene.

5. In the process for the production of hydrogenated material by hydrogenating polymeric material selected from the group consisting of rubbery homopolymers of butadiene and copolymers of butadiene containing not over 30 percent by weight of styrene wherein said polymeric material is dispersed in methylcyclohexane and contacted with hydrogen in the presence of a finely divided nickel-kieselguhr catalyst in order to reduce the unsaturation of said polymeric material; the method of removing said catalyst comprising diluting the dispersion of said hydrogenated polymeric material, methylcyclohexane, and catalyst, with an additional quantity of methylcyclohexane, said additional methylcyclohexane being added in an amount of from 1:1 to 5:1 based on the volume of said dispersion; heating the resulting mixture at a temperature of 100 to 575 F. for 10 minutes to 8 hours, the time of said heating being sufficiently long to cause agglomeration of said catalyst, and removing said catalyst from the reaction mixture.

6. In the process for the production of hydrogenated material by hydrogenating polymeric material selected from the group consisting of rubbery homopolymers of butadiene and copolymers of butadiene containing not over 30 percent by weight of styrene wherein said polymeric material is dispersed in a cycloparaffinic hydrocarbon solvent, said solvent being used in an amount to give a solution containing 3 to 15 percent by weight of said polymeric material, and contacted with hydrogen in the presence of a finely divided nickel-kieselguhr catalyst in order to reduce the unsaturation of said polymeric material; the method of removing said catalyst comprising diluting the dispersion of said hydrogenated polymeric material, solvent, and catalyst with cycloparatiinic hydrocarbon solvent, said additional cycloparatfinic hydrocarbon solvent being added in an amount of from 1:1 to 5 :1 based upon the volume of said dispersion; heating the resulting mixture at a temperature in the range of 100 to 575 F. for minutes to 8 hours, said heating being sufiiciently long to cause agglomeration of said catalyst; and removing said catalyst from the resulting mixture.

7. The process of claim 6 in which said heating is conducted at a temperature of 300 to 400 F. for 30 minutes to 4 hours.

8. In the process for the production of hydrogenated material by hydrogenating polymeric material selected from the group consisting of rubbery homopolymers of butadiene and copolymers of butadiene containing not over 30 percent by weight of styrene wherein said polymeric material is dispersed in methylcyclohexane, said methylcyclchexane being used in an amount to give a solution containing 3 to percent by Weight of said polymeric material, and contacted with hydrogen in the presence of a finely divided nickel-kieselguhr catalyst in order to reduce the unsaturation of said polymeric material; the method of removing said catalyst comprising diluting the dispersion of said hydrogenated polymeric material, methylcyclohexane, and catalyst with methylcyclohexane, said additional methylcyclohexane being added in an amount of from 1:1 to 5:1 based upon the volume of said dispersion; heating the resulting mixture at a temperature in the range of to 575 F. for 10 minutes to 8 hours, said heating being sufficiently long to cause agglomeration of said catalyst; and removing said catalyst from the resulting mixture.

9. In the process for the production of hydrogenated material by hydrogenating polymeric material selected from the group consisting of rubbery homopolymers of butadiene and copolymers of butadiene containing not over 30 percent by weight of styrene wherein said polymeric material is dispersed in methylcyclohexane to give dispersion containing approximately 5 percent of said polymeric material on a weight basis, and contacted with hydrogen in the presence of a finely divided nickelkieselguhr catalyst in order to reduce the unsaturation of said polymer; the method of removing said catalyst comprising diluting the dispersion of hydrogenated polymeric material, methylcyclohexane, and catalyst with additional methylcyclohexane, said additional methylcyclohexane being used in an amount to give a volume dilution ratio of approximately 2: 1, heating the resulting mixture at approximately 300 F. for 4 hours; and removing said catalyst from the resulting mixture.

References Cited in the file of this patent FOREIGN PATENTS 652,566 Great Britain Apr. 25, 1951 

1. IN THE PROCESS FOR PRODUCTION OF HYDROGENATED MATERIAL BY HYDROGENATING POLYMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF RUBBERY HOMOPOLYMERS OF BUTADIENE AND COPOLYMERS OF BUTADIENE CONTAINING NOT OVER 30 PERCENT BY WEIGHT OF SYTRENE WHEREIN SAID POLYMERIC MATERIAL IS DISPERSED IN A CYCLOPARAFFINIC HYDROCARBON SOLVENT AND CONTACTED WITH HYDROGEN IN THE PRESENCE OF A FINELY DIVIDED NICKEL-KIESELGUHR CATALYST IN ORDER TO REDUCE THE UNSATURATION OF SAID POLYMERIC MATERIAL; THE METHOD OF REMOVING SAID CATALYST COMPRISING DILUTING THE DISPERSION OF SAID HYDROGENATED POLYMERIC MATERIAL, SOLVENT, AND CATALYST, WITH AN ADDITIONAL QUANTITY OF A CYCLOPARAFFINIC HYDROCARBON SOLVENT, SAID ADDITIONAL CYCLOPARAFFINIC SOLVENT BEING ADDED IN AN AMOUNT OF 1:1 TO 5:1 BASED ON THE VOLUME OF SAID DISPERSION; HEATING THE RESULTING MIXTURE AT A TEMPERATURE OF 100 TO 500*F. FOR 10 MINUTES TO 8 HOURS, THE TIME OF SAID HEATING BEING SUFFICIENTLY LONG TO CAUSE AGGLOMERATION OF SAID CATALYST, AND REMOVING SAID CATALYST FROM THE HEAT-TREATED MIXTURE. 